Folding / vehicle-mounted curved screen explosion-proof photosensitive paint with photoetching patterning and double self-repairing functions and preparation and application method thereof

Abstract

The application discloses a self-repairing explosion-proof photosensitive coating for display screens and a preparation and photolithography application method thereof. The coating takes reversibly disulfide bond modified polyurethane acrylate as a main body, and is compounded with multifunctional acrylic monomers, a photoinitiator, 1-5 mu fine self-repairing microcapsules and additives. The application combines the dual mechanisms of disulfide bond intrinsic repair and microcapsule instant repair, and the microcapsules avoid visible light scattering, and the light transmittance is over 90%. The elongation at break of the coating is over 80%, and the coating is suitable for foldable screens and 3D vehicle-mounted curved screens. The system has ultraviolet lithography patterning capability, and is matched with a spray-pre-baking-exposure-development-post-baking mass production process, and solves the technical defects of poor light transmittance, incapability of photolithography, weak repairability and easy cracking of curved surfaces of traditional protective coatings, and is suitable for flexible display and vehicle-mounted central control large screen surface explosion-proof protection.

Description

Technical Field

[0001] This invention belongs to the technical field of functional polymer photosensitive materials and flexible display protective coatings. Specifically, it relates to a high-transmittance, self-healing, explosion-proof photosensitive coating suitable for foldable flexible screens and vehicle-mounted 3D curved central control displays. It also relates to the supporting preparation process and photolithographic patterning method of the coating. Background Technology

[0002] With the increasing popularity of foldable screen phones and 3D curved screens in automobiles, the protective coatings on the screen surface face multiple risks of failure, including stress concentration from bending, scratches from hard objects, and temperature shocks. Currently, most commercially available explosion-proof films use PET as the base material and are bonded with optical adhesive. Once scratched, these films cannot repair themselves, and with long-term use, micro-cracks are prone to form at the creases, which can eventually lead to the entire screen becoming unusable.

[0003] To address the scratch repair problem, existing technologies have introduced microcapsule self-healing coatings or intrinsically self-healing resins containing dynamic covalent bonds. However, traditional microcapsule self-healing materials typically have particle sizes of 20–50 μm, which induce strong Mie scattering after coating, leading to a sharp drop in transmittance and large-area Mura bright and dark spots, completely failing to meet the stringent optical requirements of display panels. On the other hand, polyurethane coatings relying solely on dynamic covalent bonds (such as Diels-Alder bonds or disulfide bonds), while possessing the potential for repeated repair, often exhibit low repair efficiency at room temperature or under mild heating. Furthermore, most of these coatings lack ultraviolet lithography patterning capabilities, making them difficult to integrate into the precision patterning processes of display panels.

[0004] Furthermore, ordinary polyurethane or acrylate protective coatings are limited by the inherent contradiction between crosslinking density and flexibility. In folded or 3D high-curvature bonding scenarios, their elongation at break is generally insufficient, making them highly susceptible to peeling and cracking under bending or thermal shock. In summary, current display protective materials cannot simultaneously achieve the four core indicators of high light transmittance, long-lasting multi-mechanism self-healing, fine lithographic patterning, and high flexibility and impact resistance. This has become a technological bottleneck that the flexible automotive display industry urgently needs to overcome. Summary of the Invention

[0005] (a) The technical problem to be solved by the present invention

[0006] The present invention aims to overcome the shortcomings of existing self-healing explosion-proof films, such as poor optical performance, lack of photolithographic processing, single repair mechanism and insufficient flexibility, and provides a photosensitive coating and its supporting application process that combines intrinsic dynamic repair and microcapsule physical repair and is suitable for panel photolithography production lines.

[0007] (II) Technical Solution

[0008] 1. A self-healing explosion-proof photosensitive coating for display screens, comprising the following essential components by weight:

[0009] (1) Modified polyurethane acrylate resin containing reversible disulfide bonds: 35-55 parts;

[0010] (2) Multifunctional acrylate monomer: 15-30 parts;

[0011] (3) Composite photoinitiator: 2-6 parts;

[0012] (4) Surface-modified fine self-healing microcapsules: 5-12 parts;

[0013] (5) Organic solvent: 10-25 parts;

[0014] (6) Functional additives: 0.1–2 parts;

[0015] The D50 particle size of the fine self-healing microcapsules is strictly controlled between 1 μm and 5 μm; the modified polyurethane acrylate resin can undergo a dynamic disulfide bond exchange reaction under thermal stimulation at 50-80℃ to achieve crosslinked network reconstruction.

[0016] 2. A method for preparing fine self-healing microcapsules suitable for the above-mentioned coatings:

[0017] The preparation method of the fine self-healing microcapsules is as follows: Low molecular weight bisphenol A epoxy resin (E-51) and a latent curing agent (modified dicyandiamide) are mixed at a mass ratio of 3:1 as the core material, and an appropriate amount of reactive diluent is added to adjust the viscosity. Melamine and formaldehyde are prepolymerized at a molar ratio of 1:3 under weakly alkaline conditions to form a capsule wall prepolymer. Using an in-situ polymerization method, the core material is emulsified and dispersed in an aqueous phase containing a surfactant. The emulsification speed is controlled to 5000–8000 rpm to refine the oil phase droplets to the target particle size (1–5 μm). Subsequently, the capsule wall prepolymer is slowly added, and the temperature is raised to 60–70℃ for a curing reaction of 3–4 hours. After washing and drying, the initial microcapsule product is obtained. To enhance its dispersion stability in coating systems, the microcapsules were surface-modified with γ-glycidoxypropyltrimethoxysilane (KH-560). The microcapsules were stirred in an ethanol / water mixed solvent at 60°C for 2 hours, and then filtered and dried to obtain the surface-modified fine self-healing microcapsules.

[0018] 3. Preparation method of coating:

[0019] Step 1: Mix the disulfide bond modified polyurethane acrylate resin with an organic solvent and stir at a constant temperature of 30-40°C until completely dissolved;

[0020] Step 2: Add the multifunctional acrylate monomer and composite photoinitiator in the dark, and shear and stir for 2 hours in the dark to form a uniform photosensitive base liquid;

[0021] Step 3: Under high-speed shearing at 3000-5000 rpm, slowly add fine microcapsules in batches, controlling the shearing force to prevent capsule rupture and leakage;

[0022] Step 4: Allow the mixture to stand at 5-10℃ for 12 hours to remove bubbles, then filter using a 1.0μm precision filter membrane to remove impurities and broken capsules, thus obtaining the finished photosensitive coating.

[0023] 4. Photolithographic patterning application methods:

[0024] The steps for forming explosion-proof films for flexible screens and 3D curved glass substrates are as follows:

[0025] S1: Ultrasonic spray coating, which evenly sprays the coating onto the surface of a transparent substrate (flexible PI / 3D curved glass);

[0026] S2: Precision pre-baking, baking at 80-100℃ for 90-180 seconds, controlling the residual solvent rate of the film layer to 4%-7%;

[0027] S3: Selective UV exposure, using a mask for 365nm UV exposure, with an exposure dose of 200-300mJ / cm², to achieve patterned curing of the photosensitive layer;

[0028] S4: Development and shaping, the developer washes away the unexposed areas to obtain a fine-edge, pixel-level protected pattern;

[0029] S5: High-temperature post-baking curing, bake at 120-130℃ for 30-40 minutes to fully cross-link and form a high-toughness explosion-proof coating.

[0030] (III) Beneficial Effects of the Invention

[0031] This invention achieves immediate filling and long-term repeated repair of scratches through the synergistic effect of an intrinsic dynamic disulfide bond and a fine microcapsule system. Testing (scratch width closure rate was quantitatively evaluated using optical microscopy) showed that, in the examples, a 2μm deep scratch, after heating at 60℃ for 10 minutes, achieved a scratch width closure rate of over 90%, far superior to the immediate repair efficiency of a single microcapsule system.

[0032] In terms of optical performance, thanks to the strict control of the microcapsule D50 within 1 to 5 μm, the strong scattering range of the visible light band (380 to 780 nm) is effectively avoided. The total light transmittance of the cured coating (tested according to GB / T2410) reaches over 90%, eliminating the white haze and mura defects caused by traditional large-particle capsules.

[0033] In terms of mechanical flexibility, this invention selects a polyurethane skeleton with disulfide bonds containing flexible soft segments and combines it with multifunctional acrylates to form a moderately cross-linked interpenetrating network. With the addition of submicron-sized microcapsules uniformly dispersed in the matrix, the elongation at break of the coating (tested according to GB / T528) reaches more than 80%, which is sufficient to keep up with the dimensional deformation of flexible PI substrates or 3D large curvature glass under folding and thermal shock without peeling or falling off.

[0034] Furthermore, the acrylic unsaturated double bond and photoinitiator system introduced in the coating formulation of this invention are perfectly compatible with the existing ultraviolet lithography process for semiconductor display panels. Customized processing of protective patterns with steep edges and micron-level precision can be achieved through mask exposure and development, expanding the application flexibility of self-healing explosion-proof materials in the field of precision bonding of display modules. The raw materials for each component of this invention are readily available, and the preparation process does not require high temperature and high pressure; mass production can be achieved through low-temperature and low-speed stirring, making it suitable for integration into existing automotive screen and foldable screen production lines. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the microstructure of a fine self-healing microcapsule. The figures are labeled: 1-melamine-formaldehyde resin capsule wall; 2-epoxy + latent curing agent core material; 3-fine self-healing microcapsule.

[0036] Figure 2 The diagram shows the cross-section of the coating and the dual self-healing mechanism. The labels are: 1-transparent substrate; 2-explosion-proof photosensitive curing coating; 3-disulfide bond dynamic cross-linking network; 4-microcapsule; 5-external force scratch; 6-microcapsule release of repair fluid. Detailed Implementation

[0037] Synthesis of disulfide-modified polyurethane acrylate resin: 100g of polytetrahydrofuran ether diol (PTMEG, Mn=2000) and 44.4g of isophorone diisocyanate (IPDI) were reacted at 80℃ for 2h. 11.5g of 2-hydroxyethyl disulfide was added for chain extension, and then 11.6g of hydroxyethyl acrylate was added for end capping to obtain the target resin.

[0038] Example 1 (Optimal Implementation)

[0039] Formula: 45g of disulfide bond modified polyurethane acrylate resin (self-made, soft segment is polytetrahydrofuran ether diol, Mn=2000), 20g of DPHA monomer, 3g of TPO photoinitiator, 24g of PMA solvent, 5g of KH-560 surface-modified microcapsules with D50=2.5μm, and 0.1g of BYK-333 leveling agent.

[0040] Preparation process: Following the steps described above, the microcapsules were sheared and dispersed at 3500 rpm, allowed to stand at 8°C for 12 hours to degas, and then filtered through a 1.0 μm filter membrane.

[0041] Application process: Ultrasonic spraying on 3D automotive curved glass, pre-baking at 90℃ for 90s (residual solvent measured at 5.2%), 365nm UV exposure (250mJ / cm²), development followed by baking at 130℃ for 30min, resulting in a final dry film thickness of 25μm.

[0042] Actual performance test data (with test benchmarks):

[0043] Total light transmittance (GB / T2410-2008): 91.8%;

[0044] Elongation at break (GB / T1040.3-2006, dumbbell-shaped cutter): 86%;

[0045] Scratch self-healing performance: A scratch with a depth of about 2μm was made on the coating surface by applying a 500g load with a 3H pencil. The surface was placed on a 60℃ constant temperature heating table and left to stand for 10 minutes. The scratch width closure rate was 94.6% as observed by a metallographic microscope. The scratches were basically disappeared by the naked eye and there was no attenuation of light transmission.

[0046] Comparative Example 1 (Verifying the necessity of microcapsule size limitation)

[0047] The only difference was that the microcapsules were replaced with traditional large-particle-size capsules with a D50 of 25 μm; everything else remained the same as in Example 1. Results: The film was severely cloudy and whitish, with a transmittance (same as standard) of only 74.2%, and exhibited large-area Mura optical distortion, making it unusable for optical inspection by the display module. This demonstrates that a particle size range of 1–5 μm is a key technical feature for ensuring optical transparency.

[0048] Comparative Example 2 (Verifying the necessity of disulfide bond resin)

[0049] The main resin was replaced with a commercially available aliphatic polyurethane acrylate without disulfide bonds, while the rest of the formulation and microcapsule addition remained unchanged. Results: The elongation at break was only 58%, and obvious microcracks and localized peeling appeared at the edges in the curved surface bonding bending test (R=5mm, 180° bend). In the scratch test, due to the lack of thermal reforming ability of disulfide bonds, relying solely on microcapsule rupture for repair, the scratch width closure rate was only 15%. This demonstrates that the resin structure containing disulfide bonds is the core foundation for achieving long-lasting, repeatable, and efficient repair.

[0050] Comparative Example 3 (verifying the necessity of surface modification)

[0051] The microcapsules were mixed directly using the same process without KH-560 surface modification. Results: During the shearing preparation process, the microcapsules severely agglomerated, resulting in a significant decrease in the actual microcapsule content in the coating after filtration. Although the cured coating achieved the required light transmittance (90.2%), the scratch test showed extremely uneven microcapsule distribution and no response from the repair fluid in some areas, leading to a scratch width closure rate fluctuating between 40% and 65%, indicating extreme instability. This demonstrates that surface modification is a necessary means to ensure uniform and stable dispersion of microcapsules under high-speed shearing, thereby achieving reliable repair.

Claims

1. A self-healing explosion-proof photosensitive coating for display screens, characterized in that, The product is composed of the following components by weight: 35-55 parts of modified polyurethane acrylate resin containing reversible disulfide dynamic covalent bonds; 15-30 parts of multifunctional acrylate monomers; 2-6 parts of composite photoinitiator; 5-12 parts of surface-modified fine self-healing microcapsules; 10-25 parts of organic solvent; and 0.1-2 parts of functional additives. The fine self-healing microcapsules have a D50 particle size of 1 μm-5 μm. The modified polyurethane acrylate resin skeleton introduces reversible disulfide bonds, which can undergo dynamic exchange and reconstruction of the crosslinked network under thermal stimulation at 50-80℃.

2. The self-healing explosion-proof photosensitive coating for display screens according to claim 1, characterized in that: The fine self-healing microcapsule has a melamine-formaldehyde resin wall and a two-component repair agent consisting of low molecular weight epoxy resin and a latent curing agent as the core material.

3. The self-healing explosion-proof photosensitive coating for display screens according to claim 1, characterized in that: The multifunctional acrylate monomer is dipentaerythritol hexaacrylate or pentaerythritol tetraacrylate.

4. A method for preparing a self-healing explosion-proof photosensitive coating for a display screen according to any one of claims 1 to 3, characterized in that, It includes the following steps: 1) Mix the modified polyurethane acrylate resin with an organic solvent and stir at 30-40°C until completely dissolved; 2) Add the multifunctional acrylate monomer and photoinitiator in the dark, and stir under shear for 2 hours; 3) Add fine self-healing microcapsules slowly in batches under high-speed shearing at 3000-5000 rpm; 4) Allow the coating to stand at 5-10℃ for 12 hours to remove bubbles, then filter through a 1.0μm filter membrane to obtain the finished coating.

5. A method for patterning the self-healing explosion-proof photosensitive coating for curved / flexible displays as described in any one of claims 1 to 3 in explosion-proof films for curved / flexible displays, characterized in that... The steps are as follows: S1: Ultrasonic spraying applies coating to the surface of a transparent substrate; S2: Pre-dry at 80-100℃ for 90-180 seconds, controlling the residual solvent content of the film layer to 4%-7%; S3: Selective exposure to 365nm ultraviolet light using a photomask; S4: Rinse with developer to remove unexposed areas and obtain a protective pattern; S5: Bake at 120-130℃ for 30-40 minutes to achieve complete cross-linking and curing to obtain the explosion-proof coating.

6. The coating according to claim 1, characterized in that: After curing, the coating has a light transmittance of ≥90% and an elongation at break of ≥80%. After heating at 60℃ for 10 minutes, the width closure rate of a 2μm deep scratch is ≥90%.

Images